Durham, N.C. — Police on Thursday said at least three people have been robbed in Durham in recent weeks while meeting someone to buy or sell goods.

Investigators call the crimes “robberies by appointment" because the victims agreed online or through social media to meet with the people who wound up robbing them.

A man told police that he went to the 400 block of Discovery Way Dec. 21 to purchase a discounted iPad from a man he had met earlier at a flea market. The seller pulled up in a green Toyota Camry, pulled out a gun and took the man’s keys and phone.

On Dec. 15, a man who had posted an advertisement on Craigslist to sell phones met a potential buyer in a parking lot in the 100 block of West Morgan Street. When the man pulled out the phones, the potential buyer pepper sprayed him and took the phones, police said.

The robbery was similar to one that occurred on Nov. 21 at the same location, police said. In that case, the suspect fled in a 2011 tan Toyota Camry.

Police said there have been several similar incidents reported in Durham this year.

They advise people who are meeting strangers to buy or sell items to meet in a public place during the day and either have a friend accompany them or tell someone where they are going. Other tips include save all communications with the buyer or seller and not to carry a lot of cash or divulge personal information.

Anyone with information about the robberies is asked to call Crime Stoppers at 919-683-1200.